In-mold decoration molding is used for producing injection-molded articles with patterns. An in-mold decoration molding method includes the steps of: disposing a pattern of a decorated sheet in a molding space (cavity) formed in molds serving as forming dies; injecting molten resin into the molding space; and removing a molded article (product) from the molding space. According to the in-mold decoration molding method, the pattern held on the decorated sheet is transferred to the surface of the molded article in a resin injection molding process. Thus, the molded article is obtained with decoration. A typical in-mold decoration molding process includes the following steps:
First, a roll of a decorated sheet is prepared. The decorated sheet includes a base sheet and a transfer layer disposed on the base sheet. The transfer layer includes a decorated layer having a printed pattern. The transfer layer may include a functional layer stacked on the decorated layer. The functional layer may be adjacent to the decorated layer, or another layer may be interposed between the decorated layer and the functional layer.
Subsequently, the long decorated sheet is fed between an opened movable mold and an opened stationary mold. When the movable and stationary molds are closed, the pattern held on the decorated sheet is disposed at a position corresponding to a molding space formed between the movable mold and the stationary mold.
After that, a clamping member is moved to hold the decorated sheet on the parting face of the movable mold, and then the decorated sheet is sucked to the cavity face of the movable mold.
The movable mold is then moved into contact with the stationary mold (closed). After that, a predetermined amount of molten resin is injected into the molding space formed between the movable mold and the stationary mold.
Subsequently, the resin injected into the molding space is cooled. This solidifies the resin into a molded article. The movable mold is then moved away from the stationary mold (opened). At this point, the transfer layer is peeled from the base sheet and then is transferred to the surface of the molded article. Thus, the decorated layer or the decorated layer and the functional layer in the transfer layer are transferred to the surface of the molded article.
Finally, the molded article is removed from the opened molds. The surface of the molded article is decorated with the pattern printed on the decorated layer.
For example, Japanese Patent Laid-Open No. 2011-025531 discloses a molding machine for realizing the typical in-mold decoration molding process. FIGS. 6A and 6B illustrate the molding machine described in Japanese Patent Laid-Open No. 2011-025531. Specifically, FIG. 6A is a cross-sectional view schematically illustrating the molding machine described in Japanese Patent Laid-Open No. 2011-025531. The molding machine in FIG. 6A includes a pair of molding/decorating dies 60 serving as shaping dies for injection molding of resin materials. The pair of molding/decorating dies 60 includes an A die 61 and a B die 62. FIG. 6B is a schematic plan view illustrating a part face (parting face) 63 of the A die 61.
The molding machine illustrated in FIGS. 6A and 6B includes a clamping member 64 and a sheet feeder 70. The sheet feeder 70 includes a sheet roll 71 and a winding roll 72. The sheet feeder 70 feeds a decorated sheet 73 from the sheet roll 71 to the winding roll 72 when the pair of molding/decorating dies 60 is opened. Thus, a pattern 73a held on the decorated sheet 73 is disposed between the A die 61 and the B die 62. When the pattern 73a is positioned, the clamping member 64 presses the decorated sheet 73 to the part face 63 of the A die 61.
When the clamping member 64 holds the decorated sheet 73 on the part face 63 of the A die 61, the decorated sheet 73 is sucked to a cavity face 65 of the A die 61. After that, the A die 61 and the B die 62 are closed. This allows the pair of molding/decorating dies 60 to contain the decorated sheet 73.
Subsequently, molten resin is injected onto the contained decorated sheet 73 from an injection port 66 formed on the B die 62. Thus, the injected resin fills a molding space formed in the pair of closed molding/decorating dies 60.
The molten resin injected into the molding space is cooled and thus is solidified into an injection-molded body (molded article). When the resin is solidified, the A die 61 and the B die 62 are opened. At this point, the transfer layer is peeled from the decorated sheet 73 and is transferred to the surface of the injection-molded body.
When the A die 61 and the B die 62 are opened, the decorated injection-molded body is removed from the pair of molding/decorating dies 60. As has been discussed, the transfer layer includes the decorated layer having the printed pattern 73a and thus the pattern 73a is transferred to the surface of the removed injection-molded body. A layer (transfer layer) formed by transfer to the surface of the injection-molded body may have a multilayer structure in which a functional layer or the like is stacked on the decorated layer with a printed pattern so as to provide functions, e.g., UV protection for the surface of the injection-molded body.
In in-mold decoration molding, a pattern held on a decorated sheet needs to be transferred to the surface of a molded body (molded article) with high positioning accuracy such that the molded article is decorated with an excellent appearance. Thus, it is important to align the pattern of the decorated sheet and the cavity face of the die. For example, as described in Japanese Patent Laid-Open No. 10-034704, a positioning mark printed beforehand on a decorated sheet is detected by a camera or a sensor to position the pattern of the decorated sheet.